What could be causing an Invalid Client error message when using SSO for Hubshare?

Hi, 

We have been using SSO for a number of months and now out of nowhere we get this error message: "An error ocurred while trying to authenticate through SSO: invalid client"

The secret code should be valid until the end of april

Our Technology team is investigating, but it would be grateful if you could help us diagnose the problem

Many thanks

Irene